Thesis (M.Eng.) - Asian Institute of Technology, 1993

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering.

Beach berm and even dunes eroded under storm wave with high water level, will cause material to remove offshore to form a far parallel to the beach, and reach almost the final shape at some ultimate location. Actually wave heights and wave period vary continuously during the storm period, but as a first step of engineering approach, only the fix storm wave heights and period are used to estimate how these wave characters affect bar positions and heights during the course of a storm. This study aim to use the semi-emperical relationship of sediment transport rate propsed by Larson and Kraus (1989) to visualize the incipient formation, growth and movement of a bar during storm period and also to estimate the retreat of foreshore beach under storm action.It is found from the present numerical modeling, that comparing the computed and measured beach profile for 0.22 mm and 0.40 mm sand diameter, it gives good agreement especially at the final state. Model improvement was conducted by two approach, firstly the shape parameter of equilibrium beach profile is substituted by the new relationship with the dimensionless fall velocity and then it can provide better simulation of bar size and location. Secondly the time-dependent of sediment transport rate coefficient is newly proposed and found to be more realistic to the profile of initial state of bar development. Lastly the bar developing and always moving offshore with different speed as time increasing.